ACX plywood has grade “A” face and grade “C” back the “X” standards for exposure. ACX plywood is a version of a plywood panel that has a very specific. It is often extended beyond traditional wooden plywood to include medium density fiberboard (MDF), particleboard, hardboard and chipboard. Amongst the many kinds of plywood available, is ACX plywood. All grade-stamped Arauca Ply panels are manufactured in accordance with the US PS1-09 product standard and all ACX products are PS1-09 underlayment. First letter in the abbreviation stands for the front side, the second is the reverse side which usually poorer finish.